Parameter analysis of impedance pharyngography (IPG) for assessment of swallowing function

With steady aging of society, the number of patients with dysphagia due to esophageal cancer and to muscular and neural diseases is increasing. This tendency is a problem from the viewpoint of social welfare. We intended to develop a simple quantitative evaluation method for the swallowing function, and we propose impedance pharyngography (IPG), which can measure noninvasively the electrical impedance of the neck during swallowing. Although the swallowing function is reflected in the IPG, the effect of swallowing function degradation on the waveform varies depending on the cause of the problem, making it difficult to compare simply the IPGs of subjects with various states of the swallowing function. In this study, four parameters are defined, based on the normal IPGs of normal young subjects, in order to evaluate the waveform features representing the swallowing function, namely, the pharynx transit time, the rate of impedance change, the similarity, and the timing of the swallowing sound. Then, a method is proposed to evaluate the IPG quantitatively. IPGs of two groups, young and elderly, are analyzed in terms of these parameters, and it is shown that the degradation of the lifting speed and the lifting distance of the larynx, and also degradation of smooth activity of the organs related to swallowing, can be detected as differences in the parameters.